Page 75 - Programming the Photon Getting Started With the Internet of Things

Schematic Reference Description Appendix

M1 Photon board M1

Breadboard H1

Jumper wires H2

D1 5-mm LED S1

R1 220-ohm resistor R1

Table 4.2 Components and Hardware

With all types of LEDs, the current only flows in one direction: from the anode to the
cathode. As a result, the anode should always be connected to power source. In our
instance, this will be the voltage output from the digital pin on the Photon board, which is

3.3 V. When using LEDs, it is also common to see them run in series with a resistor.
Resistors are not polarized; therefore, you do not need to worry about how they are
connected to the circuit. Table 4.2 shows the components we will be using for this
experiment.

You will need to connect the LED to pin D0 on the Photon board; you can do this by

inserting the LED into the breadboard as shown in Figure 4.3. Don’t forget that we also
need to connect a resistor in series to act as a current limiter, which will prevent damage to
the LED or the Photon board. The larger the resistor value, the more it will restrict the
flow of current and the dimmer the LED will glow. Connect the resistor to pin D0 and the

other end to the anode of the LED (the longest leg). Take a jumper wire and connect the
cathode leg of the LED to the GND pin on the Photon board (refer to Figures 4.3 and 4.4
to see how to wire the circuit).